# Tangential Quadrilateral

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In geometry, a **tangential quadrilateral** is a convex quadrilateral whose sides are all tangent to a single circle within the quadrilateral. Sometimes it is called a tangent quadrilateral, circumscribed quadrilateral, or circle inscribed in a quadrilateral. The circle is called the incircle of the quadrilateral or its inscribed circle. The center of the circle is called the incenter and its radius is called the inradius.

## Theorems

According to Pitot's theorem, the two sums of the lengths of opposite sides are equal.

A circle can be inscribed in a quadrilateral if and only if the angle bisectors of the four angles of the quadrilateral are concurrent.

**Cite as:**Tangential Quadrilateral.

*Brilliant.org*. Retrieved from https://brilliant.org/wiki/tangential-quadrilateral/